actually I do not understand what you said...I need final concentration in mouse is 10 micromol/kg, and nothing moreI dont know how much I should take chemical and how much volume from this solution I should administer into mouse (if mouse weight is 30 gramm) .....

The usual way to “dose” an animal is to administer so much substance per kg body weight. There is no such concentration as a “micromole/kg” like there is a mole/L. As I understand the problem, you need to administer 30 micrograms of a 100 MW compound to a 30 gm mouse to be giving a dose of 10 micromole/kg (of body weight of the mouse). Unless I’m missing something.

How much volume of stock solution you need to use to get 30 micrograms of compound depends on the concentration of the stock solution, not on the weight of the mouse. You will need to adjust the dose depending on the weight of the mouse—a little more if the mouse weighs more than 30 grams, or a little less if it weighs less than 30 grams. But it makes no sense to be talking about the “volume” of a mouse. (Well, technically you can estimate the blood volume and distribution space of the mouse, but that is only an estimate and I suspect beyond the scope of this problem unless your course is heavily into pharmacokinetics or pharmacodynamics.)